I'm not absolutely sure this is a bug, but it looks like it...

(defclass foo ()
  ((bar :accessor cons)))

gives an error about defining an accessor function with a name already
assigned to a function. If you change the definition after clearing
the error and re-evaluate,

(defclass foo ()
  ((bar :accessor bar)))

you still get the same error: "CONS already names an ordinary macro or
function".

Chris Capel